Information (IT) systems are required to continuously make available services that the systems provide without anxiety. The information systems substantially increase in scale and take a very important role as social infrastructure, so that, once an accident occurs, the whole nation, or in some cases throughout the world, is affected by it. There is a case where a serious failure is caused in banking systems, communication systems, railway systems, and cloud systems, which leads to a huge amount of compensation. Stakeholders bear in mind that, if a large accident occurs, liabilities are pursued, and if negligence is admitted, a harsh penalty is imposed.
With regards to reliability, availability, maintainability, safety, completeness, and confidentiality of computer systems, dependability has been discussed for a long time as properties that computers need to include (for example, see Non Patent Literature 1). In the development of embedded systems, a technique has been applied wherein a development project is drawn up at first, and functional requirements and non-functional requirements for target systems and services are established as a specification, and verifications and tests are conducted over a long period of time and deployed. However, the number of failures has been increased day by day. In the standards such as CMMI and ISO 26262, they have been attempted to reduce human errors. However, these existing technologies and standards lack consideration for the characteristics of the systems in the open environment.
Accordingly, Japan Science and Technology Agency (IST), which is an independent administrative institution, started the DEOS project as one of CREST programs in 2006, which is aimed at consolidating, institutionalizing, and further commercializing a system of techniques that guarantee the dependability of information systems. If this system of techniques is expressed in a word, it can be described as a system of techniques in which the safety standard of systems is defined, and when the safety standard of systems is deviated, abnormal situations are avoided before running into abnormal situations, or even when the system is run into abnormal situations, immediate recovery can be applied, which the inventors and the like define as open system dependability (Open Systems Dependability).
This open system dependability is classified in view of process and consolidated as DEOS process (for example, see Non Patent Literature 2 and Patent Literature 1). If the characteristics of the DEOS process is expressed in a word, it can be described as a process that regulates the behavior of persons and objects according to the target systems in order to guarantee the open system dependability according to the entire life cycle regarding the target system ranging from planning and designing on the upstream to operations, which maintains the normal operational states of the target system with agreements with regards to every argument as a base, which includes an agreement with regards to requirements for the target system from persons (stakeholders) who engage in the target system. D-Case is designed as a common language between respective processes (for example, see Non Patent Literature 3).